1. Field of the Invention
The present invention relates to a device for assembling and adjusting an optical pickup or similar optical unit.
2. Description of the Background Art
Generally, an optical pickup includes a laser diode (LD) or similar light emitting element, an object lens for converging light issuing from the laser diode, a photodetector to which a reflection from a disk is incident, and various optical parts arranged on an optical path extending from the laser diode to the disk. The optical pickup selectively records or reproduces information in or out of the disk. It is a common practice with the optical pickup to package the laser diode, a hologram element and the photodetector into an HOE-LD (Hologram Element-Laser Diode) unit assembled and adjusted beforehand. This promotes easy assembly and adjustment of the optical pickup.
The prerequisite with the HOE-LD unit is that the laser diode, hologram element and photodetector be accurately positioned relative to each other. To adjust the relative position, optics equivalent to or comparative in effect with the optics of the optical pickup may be used, as proposed in the past. In this case, assembly and adjustment are effected by using light issuing from the laser diode of the unit as a reference.
Japanese Patent Laid-Open Publication No. 8-111026, for example, discloses an adjusting device for an optical pickup including a light emitting element, a photodetector, a collimator lens, a reflection surface, an object lens, and an optical device made up of a diffraction grating and a hologram element. A reflection derived from light issuing from the light emitting element is incident to the photodetector. The collimator lens collimates the light issuing from the light emitting element to thereby output parallel rays. The reflectIon surfaced reflects the light issuing from the light emitting element. The optical device inputs the light from the light emitting element to the object lens while inputting the reflection from the reflection surface to the photodetector.
In the prior art adjusting device described above, the collimator lens outputs ideal parallel rays while the focus of the object lens coincides with the reflection surface. In this condition, light with the maximum intensity is incident to the photodetector. The optical device made up of the diffraction grading and hologram element is rotated about the optical axis such that the same intensity of light is incident to the photodetector when the object lens is moved by +L and xe2x88x92L in the direction of optical axis. With this prior art scheme, however, it is extremely difficult to implement ideal parallel rays with the collimator lens or to adjust the optics, which is equivalent to or comparable in effect with the optics of the optical pickup, to the focus of the object lens.
It is an object of the present invention to provide a device including adjusting optics capable of easily adjusting an optical unit.
In accordance with the present invention, a device assembles and adjusts an optical unit, which includes at least one light emitting element and at least one photodetector mounted on a single case, such that the hologram element is so positioned as to implement a desired signal characteristic. The device includes a collimator lens to which a light beam output from the optical unit is incident, an autocollimator to which parallel rays output from the collimator lens are incident, and an adjusting mechanism including the collimator lens and autocollimator. The device determines the position of the light emitting element.
Also, in accordance with the present invention, a device assembles and adjusts an optical unit, which includes at least one light emitting element and at least one photodetector mounted on a single case, such that the hologram element is so positioned as to implement a desired signal characteristic. The device includes a collimator lens to which a light beam output from the optical unit is incident, a quadrisected photodetector to which parallel rays output from the collimator lens are incident, and an adjusting mechanism including the collimator lens and quadrisected photodetector. The device determines the angular deviation of the intensity distribution of the light emitting element.
Further, in accordance with the present invention, a device for assembling and adjusting an optical unit of includes an adjusting device including a collimator lens, an object lens, a disk, and a signal sensing system. A light beam output from the optical unit is incident to the collimator lens. Parallel rays output from the collimator lens are incident to the object leans. Further, a spot converged by the object lens is incident to the disk. The signal sensing system receives a light beam reflected by the disk via the object lens to thereby determine a distance between the object lens and the disk and a positional relation between the spot on the disk and the groove of the disk. The device allows the position of a light emitting element to be accurately determined and therefore allows the angular deviation of the intensity distribution of the light emitting element from a designed value to be easily grasped.